Manufacture of rayon



Feb. 13, 1945.

G. l. THURMOND MANUFACTURE of' RAYON.

Filed March l, 1939 4 Sheets-Sheetl l TWICE 5779576190?? FMA/mms' can:cria

gime/MM Feb. 13, 1945. 3` T HURMOND 2,369,190

` y MNUFACTURE oF RAYON Filed March l, 1959 4 Sheets-Sheet 2 o. my w ,ud o u. /n N wf M Feb. 13, 1945. G. 1. THURMOND v MANUFACTURE 0F RAYON 4Sheets-Sheet 3 Feb. 13, 1945. 3.` L THURMOND 2,369,190

MANUFAGTURE oF RAYON l Filed March l, 1959 4 Sheetsv-Sheet 4 A 'llerlf72101110111 'u MM Patented Feb. 13, A19.45 l

MANUFACTURE F RAYON Gubert I. ramona, Asheville, N. c., assignmtoAmericanEnka Corporation, Enka, N. G., a corporation of- DelawareApplication Maren 1, '1939, serial No. 259261 (cl. 11s-s) .6 Claims.

'Ihis invention relates to a process of and system for producing a.strong yarn or thread of synthetic filaments and to the treatment ofyarn or thread in a manner to preserve the properties thereof whenformed into a cable of the type normally used in the manufacture ofpneumatic tires,

hose, belting or reinforcements for molded and cast .plastic materialsin general of either natural or synthetic origin. More specifically theinvention contemplates the formation of improved artificial threads orfilaments formed primarily of viscose which have an unusually high4tenacity and low elongation.

In the manufacture of pneumatic tires and generally similar flexiblerubber articles it has long been the custom to utilize cotton cords forlthe reinforcement thereof. The substantially universal use ofcottonncords in the manufacture of tires has been due primarily to thefactthat such cords are not affected by heat and moisture to aprohibitive degree and that when they are formed into strands twisted ina definite manner they have the required degree of resiliency,ilexibility and tenacity. However, during recent years many tests haveshown thatcords formed of rayon may be utilized in tires and likeconstructions With even greater effectiveness than cords produced fromcotton. Nevertheless, the substitution of rayon cor-ds or cables forcotton cords in the manufacture of products of the type indicated hasbeen delayed for numerous dimculties In connection with the use of rayonin the production of cables for use as reinforcements in tires, beltsand the like, the properties of the individual filaments and of theslightly twisted yarn determine to a substantial degree the finalproperties of the cables or cords. While the strength per unit weightand elongation of the cable or cord may be markedly impaired by impropertwisting at its various stages of formation yet the ratio ofcorresponding values for filaments and cords will -be very nearlyconstant for a given were encountered which had to be more fullylovercome before rayon cords were suitable forv extensive commercialadoption.

In View of the research and other activities of the manufacturers oftires, belts and allied prody ucts there is at present a demand for highquality.' rayon threads and yarns -at a cost somewhat com-l parable withcotton, and this demand will undoubtedly increase rapidly as yarns areproduced which have a greater strength and lower elongation and whencables formed therefrom have higher flexing tests and adheresatisfactorily to rubber. Customarily tire cords are formed in threeseparate twisting operations, the basic threads which are termed yarncomprise a plurality of small filaments twisted together. A plurality ofyarns are twisted together or plied to form a structure known as a plyor intermediate strand and plies thus formed are twisted with otherplies to form a cord or cable. It has been determined that theproperties of the cable are dependent in part upon the degree of vtwistat eachv stage in the formation thereof. Preferably the yarn has a verylow degree of twist.

method of twisting. f In the manufacture of pneumatic tires, cord areimpregnated with and covered by rubber which is then vulcanized and thestrength of the tire walls is dependent to a large extent upon theproperties of the cord imbedded therein. It is clear that a strong cordis required for use in tires. However disadvantages other than thosenaturally resulting from weakness of the fiber arise from the use ofinferior cords even when formed of high quality fibers and the reasonstherefor are not so readily apparent. If there is any tendency on thepart of the cord to alter its length due to its original inferiorqualities or because of deterioration or aging,` the bond betweenadjacent cords and between the cord and rubber may be ruptured to suchextent as to render the tires practically useless. Nevertheless, thecord must have\a substantial resiliency in order to withstand the`strains normally imposed by reason of the pneumatic pressure within andof mechanical shocks applied to the exterior of the tire casing. Rayonthreads and cables known prior tothis invention do not possess asuitable combination of high tenacity, resilience and low degree ofelongation to adapt them for use' in bodies formed from plasticcompositions, such as tires, belts, and the like.

This invention contemplates the provision of a superior type 'ofartificial filaments and yarn formed thereof, which overcomes thedifficulties referred to above and which have a high tenacity and otherproperties very desirable in the production of cords for the fabricationof pneumatic tires and the like. It has as a further object theprovision of a process for the formation of laments and yarns of uniformproperties.

Additionally the invention contemplates a process of and al system forproducing a strong and extremely low elongation artificial yarn, whereinthe freshly formed filaments 4are stretched up to the breaking point,washed, and thereafterin the acid free condition they are stretched upto the breaking point as a result of which treatment a greaterstretching of the laments is obtained than has heretofore beenconsidered possible.

It is also an important object of this invention to provide a rayon cordor cable having increased resilience and very little tendency to changein length as a result of alteration in the properties thereof. A

Other objects and advantages of the present invention will be apparentfrom the following detailed description when considered in connectionwith the accompanying drawings wherein:

Figure 1 isa flow sheet setting forth the important steps of onecomplete continuous process conducted in accordance with the invention,which iiow sheet additionally sets forth an alternative interruptedprocess;

Figure 2 is a diagrammatic view of an apparatus formed in accord-ancewith this invention for producing yarn in a continuous manner;

Figure 3 is a diagrammatic view of a modified form of apparatusconstructed in accordance with this invention;

Figure 4 is a view taken on line 4 4 of Figure 3 showing the freelyrotating stretching rollers arranged in a bath through which thefilaments are propelled; i

Figure 5 is a diagrammatic view of an apparatus which includes atwisting device used in one step of the alternative interrupted processof Figure 1; and

Figure 6 is another modification shown diagrammatically of the inventionwherein the major stretching operation takes place between drivenrollers and during washing.

In referring to the drawings in detail with particular reference 'toFigure 1, it will be seen that the present invention when applied to theproduction of viscose yarn comprises generally the preparation of aviscose spinning solution of alkali and cellulose, the latter preferablycomprising at least of cotton linters. The solution is then aged,filtered and thoroughly deaerated. Such deaeration of the viscose isusually accomplished under vacuum, in which event the deaeration step ispreferably practiced by subjecting the viscose solution to pressuresabnormally low as compared with known technique 'for an abnormallyprolonged period of time. For

example, a vacuum below 20 mm. may be desirable. The spinning solutionthus treated is then delivered to spinnerets through corrosion resistantand non-contaminating conduits, spun into a novel coagulating bath andthe yarn composed of a number of filaments is thereafter stretched aplurality of times. In the spinning arrangement shown in Figure 6, theyarn is only given a slight stretch between the spinneret and firstgodet, but by virtue of the Washing action in the second bath which isonly slightly acidic, a veryl much greater stretch can be obtainedbetween the two godets than has heretofore been possible. When the yarnis stretched initially up to its breaking point while in acid conditionand then is washed and again stretched up to its breaking point while ina moist and substantially acid free condition it will have a very hightensile strength, and a low degree of elongation. However, filamentswhich are stretched to a lesser degree during either of the stretchingsteps or both will nevertheless be suited for use in tires and they willhave substantially uniform properties throughout their lengths. l

It has also been determined that very ecient results may be had if thefilaments are stretched but once providing a high degree of stretch isimparted thereto. This is particularly true if the stretching step isconducted during or subsequent to, the washing of the filaments andwhile they are still in a plastic state.

More specically as will appear from a consideration of Figure 1 of thedrawings very high quality filaments are obtained by the utilization ofa viscose solution which contains about 7.4% cellulose by weight and anequal amount of sodium hydroxide. Although the viscose solution employedaccording to this invention is characterized by a content of cellulosesubstantially equal to the amount of caustic employed therein, theproportions may be varied within rather wide limits with resultant lossof but some of the benefits of the invention. After the preparation ofthe viscose solution it is subjected to high vacuum deaeration for aprolonged period. The deaerated solution is then aged or ripened.Preferably it is ripened to or above 111A, ammonium chloride index.During the aging period the viscose solution is ltered in a ltrationapparatus composed of materials resistant to attack by components of thesolution.` A filter press may be utilized for this purpose, the framesof the press and other parts which come in contact with the solutionbeing formed of, or covered with, nickel or other suitable materialwhich will not contaminate the solution undergoing treatment. After theviscose solution has been properly ripened and it has been filtered itis passed through conduits similarly formed or lined withnoncontaminating material and it is delivered to spinnerets throughwhich it is extruded into a spinning or coagulating bath. The spinningor coagulating bath is one of high magnesium content vas it containsaccording to the preferred embodiment of the invention approximately 10%of magnesium sulphate by weight.

The filaments thus formed are then stretched and further treated toprovide a yarn having a high tensile strength, a low degree ofelongation particularly suited to the formation of tire cords and onewhich has substantially uniform properties throughout its length.

y In general the spinning bath is of somewhat conventional nature exceptas noted with respect to the magnesium content and as hereinafterspecified. Ofther components dissolved therein may include sulphuricacid, sodium sulphate, ammonium sulphate, zinc sulphate and other saltswhen desirable. Such baths, as are known in the art, give considerablediflicultyduring the spinning operation by reason of the fact that whenthey are used solids tend to accumulate in the spinneret orices andimpair the properties of the filaments. -In order to produce a yarnsatisfactory for general use frequent cleaning of the spinnerets wasfound to be necessary and this cleaning operation of the small orificesnecessarily involves costly precision work. However, this problem maynow be substantially entirely overcome and a great improvement in theproperties of the filaments produced will be had by spinning thefilaments in the presence of a dissolved material of a cation activenature. Such materials are discussed at length in United States Patent2,125,031 to Polak, et al. For example, a small quantity (0.04 per centby weight) of dodecylpyridinium chloride dissolved in the spinning batheliminates practicallyy all of the irregularities and' diiiiculties ofspinning and permits a much longer vspinning time free from the'frequent interruptions heretofore encountered for cleaning thespinneret.

The contamination of the spinnerets to an exaggerated degree has beenencountered when an ordinary viscose solution is extruded throughgold-palladium Spinnerets into a spinning bath of the type noted above.The spinnerets become seriously contaminated in a few hours and thisincurs interruption of the spinning period with resultant time andproduction losses. However, the presence of 0.1 per cent of dodecyltriethyl amonium iodide in the spinning solution reduces the tendencytoward clogging of the spinneret l orifices to a remarkable extent.

The laments formed by the extrusion step are conducted through the bathand upon being withdrawn therefrom they are given a suitable stretch,such as for example from about 30% up to the breaking point. Thefilaments are then again stretched while in moist condition from aboutup to the breaking rpoint. Between the two stretching steps thefilaments are ably washed and desulphurized or at least they arepartially washed since the intermediate washing step causes thefilaments to be stronger and to have a lower elongation than when thestep is omitted. It is surprising to note that byfollowing such aprocedure considerablyn morev stretch can be imparted to the filamentsthan has heretofore been possible. Atotal stretch can be obtained thatis substantially above 50% and it has even been determined that thefilaments vcan be stretched more than l70% of their original lengthwithout breaking. Washing and desu]- phurizing of the filaments may beaccomplished in several ways and as set'forth in the flow sheet inFigure l of the drawings the process employed may be continuous or itmay be interrupted, that is, the coagulated filaments may by thecontinuous process be stretched, then washed by being drawn 'through abath and then again stretched while by the interrupted process thefilaments are stretched and then wound upon a spool under reducedtension, whereupon the bobbin is washed by the pressure-vacuum methodyand the moist filaments are then either twisted and stretched during arewinding operation or they are merely stretched and not twisted. Cakespun yarn having been twisted during collection has to be stretchedonly.

The interrupted process permits the winding of a spool of freshly spunyarn under less tension than heretofore utilized and this facilitateseasy washing of the yarn while in spool form. During the rewinding theyarn is wound in the usual manner. Ease of washing is an importantfeature of this phase of the invention. In this connection it should benoted that while the second stretching step may be performed beforecomplete washing, such procedure then involves the washing of a tightlywound bobbin, but this is permissible because the package contains onlya small amount of residual acid from the precipitating bath.

In referring to Figs. 2 to 5 inclusive, several systems are illustratedwhich are constructed in accordance with specific features of thisinvention. Yarns having the characteristics suitable for use in themanufacture of tires and the like may be readily produced with any oneof the systems by the proper preparation and handling of the spinningsolution in the bath and by the control of the stretching operation.While artiilcial yarns other than viscose yarns may be pro- ,duced bythe methods herein disclosed with satispelled by the godet prefer- Figs.2 to 4 inclusive are of a continuous nature.

factory results, it will sumce to refer to the apparatus illustratedwhen `used in connection with the viscose process. In each of thesystems referred to, a spinneret I0 is connected to a feed pipe (notshown) through which a viscose solution properly prepared, deaerated andripened, is delivered thereto. The solution is then extruded through thespinneret into a coagulating bath II of the type referred to above, andthe yarn I2 formed of a number of filaments ls'drawn from the bath by agodet wheel I3. The `yarn is pro- I3 at the same speed as theperipheral-speed thereof and the -yarn is led one or more timestherearound to avoid slippage upon its surface. Another godet wheel Illis arranged in spaced relation to godet Wheel I3 and i/t is rotated at agreater peripheral speed than is the first godet' wheel, whereby, whenthe yarn is passed from the godet wheel I3 and is directed over andaround godet wheel It one or more times, it will of necessity bestretched between the two godet wheels, the desired degree of stretchingbeing controlled by the relative speeds of the godet wheels.

y The specific processes intended to be conducted by the utilization ofthe systems illustrated in In each of these systems a bath I5 isprovided beyond godet wheel I4 and the filaments are caused to travelthrough said bath with a resulti'ng washing, bleaching and/ordesulphurizing treatment as may be desired and effected by the properselection of the bath. Within the bath Iii the filaments are againstretched and they are thereafter conducted to and collected upon abobbin I6. 1t isof course to be understood that all of the systemsillustrated may be modified so that a centrifugal the collectingmechanism, instead of a bobbin,

yArranged within the bath, as illustrated in Fig. 2, are two godetwheels Il and IB respectively, which godet wheels are substantialduplicates o godet wheels I3 and I4. Filaments I2 are-passed from godetwheel I4 to' and around godet wheel I'I one or more times in order toavoid slippage. Godet wheel Il is preferably driven at a peripheralspeed substantially the same as that of godet wheely I t. As thefilaments are passed between godet wheel Il and to bobbin It they aredirected around godet wheel I8 one l .or more times.

The filaments in the passage through the bath are thus subjected to thedesired washing or other treatment and during the latter part of theirpassage within the bath they are given an additional stretch for thereason that while godet wheel I1 has a peripheral speed commensurate tothe peripheral speed of godet It, the peripheral speed of godet wheel I8is greater than that of godet wheels I4 andv I1. The degree ofstretching of filaments within the bath I5 is controlled bythe speed atwhich the godet wheel I8 is driven, and of course this speed may bemodified inv accordance with the degree of stretch required. I FilamentsI2 are collected on bobbin I6 under the desired tension by means of theperipheral speed'imparted to such bobbin.

The specific stretching mechanism illustrated inI Figs. 3 and 4 which iscontained in the bath I5 for the purpose of imparting. the secondstretch to the filaments I2 is of the type illustrated in the patent toHans A. Schrenk, No. 1,968,912, dated August 7, 1934. .Thismechanisminvolves an idler roller I9 and freely rotatable upper and lower rollers20 and 2I respectively. The rollers 20 and 2l are driven solely by thefilaments and pot or bucket may be used as y are provided with guidinggrooves 22 which decrease in depth toward the discharge end thereof sothat the respective diameters of the rollers at the bases of the grooveswill gradually increase from the first groove in which the filaments I2are received after they have passed from idler I9 to the last groovecontacted by the filaments on the roller 2| from which the filaments aredelivered to a driven godet wheel 23. An idler guide 24 is positionedadjacent godet wheel 23 for directing the filaments thereover and anidler 25 is positioned to receive the filaments as they are passed fromgodet wheel 23. After the filaments are passed around idler 25 they areconducted to bobbin I6 in the manner previously described with respectto the apparatus of Fig. 2. From the `description of Fig. 3 it will beclear that filaments I2 are washed or otherwise treated in bath I5before and during the second stretch and, due to the arrangement ofrollers 20 and 2|, each time that the filaments are passed from one ofvthe rollers to the other they are slightly stretched and at the sametime subjected to further treatment in the bath. This' each passage ofthe to the other results gradual stretching during filaments from oneroller from the gradual increase base of each succeeding groove 22.

The processes as conducted in the apparatus of both Figs. 2 and 3 arecontinuous. The laments are rst stretched after being extruded and theyare then washed and again stretched. The second stretching may beimparted after the filaments have been passed from the washing ortreating bath so long as the filaments are still in a plastic and moistcondition.

The system illustrated in Fig. 5 is of a noncontinuous or interruptedtype. In the system illustrated in Fig. 5 the laments as they are passedfrom godet wheel I4 are led to and around idler 26, whereupon they arepassed to the temporary bobbin 21 Where they are collected under reducedtension. It will be noted in the system as thus far described only onestretching is imparted to the filaments up to the time of collection onbobbin 21. Bobbin 21 is next subjected to a high-pressure high-vacuumwashing operation in a bath 28, which may be of the same genheretoforereferred to in connection with Figs. 2 to 4 inclusive of the drawings..`Bobbin 21 after being treated, and while the filaments are still in aplastic condition, is placed upon a stationary support and the filamentsare drawn therefrom and twisted. The filaments pass through l godetwheel 30 one or more times, and they are then passed to and around godetwheel 3|, after which they are delivered to bobbin I6 for col-` lectionin the usual and 3| are manner. Godet wheels 30 substantially the sameas godet wheels I3 and I4 and the filaments are conducted thereover in asimilar manner. In order to effect a second stretching of the filamentsas they are passed between godet wheels 30 and 3|,' wheel 3I is drivenin such a manner that its peripheral speed is increased to the desiredextent above the peripheral speed of godet'wheel 30. In the event thatthe freshly spun filaments are collected in a centrifugal bucket, thecake is made up of already twisted filaments, in which case it is onlynecessary to restretch and collect the filaments in a manner also shownin Fig. 5. It

to dry the washed bobbin or cake spun package prior to the re-stretchingoperation. The dried guide 29 and then around f' in diameter of the vthesecond stretch.v

package must then be rewetted before or during 'I'he washed bobbinpackage 21 may even be satisfactorily restretched without twisting, thetwisting step being conducted in a subsequent separate operation.When'the package 21 or 21a is restretched between the godets 30 and 3I,a certain amount o1' drying will result, especially if the twisting issimultaneously effected. If it is desired tocompletely dry the packageseither in bobbin or cake form, a drying zone can be `readily interposedbetween the last godet 3| and the take-up device I6. It has beendetermined that such treatment will result in yarn having extremelyuniform shrinkage properties throughout its length.

Referring sp'ecilcally to Fig. 6, the filaments I2 are extruded throughspinneret I0 into a coagulating bath II and thence led one or more timesaround a godet wheel 32 whereupon the filaments are conducted to anidler roller 33 1ocated in' a wash bath 34. This bath may be veryslightly acidic in order to further coagulate the effect a substanspeedthan godet wheel 32. 'I'his difference in peripheral speed imparts thedesired stretch to the' filaments which taken in conjunction with theinitial stretch in bath II, can be considerably greater than washeretofore possible by conventional methods. The filaments are thencollected on a bobbin 36 or in a pot after first passing around a secondidler roller 31.`

In the interrupted process or' in the process according to Fig. 6 inwhich a high stretch is only imparted at one stage, the threads may beco1- lected under the desired tension, Washed and dried. An additionalstretch may then be simultaneously imparted to a multiplicity of threadsafter rewetting the same and collecting at a common source such as aslasher or beam and the like. The yarn produced by the utilization ofany of the above systems in connection with the process of thisinvention has, as stated above, important application to the tire andrelated arts. An important step in the preparation of a tire cord forthe purpose of preventing loss of strength due to the twisting of thecord components involves the application of a finishing material to theyarn in at least one stage of the spinning operation. A softening agentwhich has no deteriorating effect on the yarn is utilized as thefinishing material. This is a highly important aspect of the completeprocess of this invention since it has been found that the employment ofthe finishing material will improve the final .strength of the cable byfrom 10 to 50% by preventing substantial loss in strength of the yarnduring twisting. Apparently, the employment of the finishing materialpermits the yarns and plies when twisted to assume a position of leasttension and strain and specific flexing tests have been made oh cablesformed of yarn twisted as hereinafter specified which show abnormallyhigh flexing tests as compared to yarn otherwise similar but notfinished in the same manner. Additionally, cables formed from yarnsfinished in this manner are smoother and more dense than similar cablesformed of untreated yarns and the strength thereof closely approachesthe combined strength of the individual yarns. A solution of MonopoleBrilliant oil has been found to produce excellent results when used as afinish for the yarn. However, various types of materials can beadvantageously used for this purpose and sulphonated olive oil,sulphonated castor oil, emulsiiled glyceridessuch as blown tea-seed oil,and lecithin have been found satisfactory. Sulphonated oils for thispurpose may be stabilized by the addition thereto of a small amount ofalkali such as soap and an antioxidant. l

The finishing agent may be applied to the yarn as such or as a solutionor emulsion with any suitable vehicle. Goodeffects are obtained from theaddition of a finish during washing or immediately subsequent to thewashing stage. However, application of the treating material to thedried spools of yarn with redrying prior to the twisting of the yarngives excellent "results, It has been found that 0.3% of monopole oilbased on the weight of the dry yarn Will provide one of the bestconcentrations for most purposes.l Results which have been obtainedindicate very clearly that softening agents are much better thanlubricating ilnishes in connection with yarns to be plied or plied andcabled and then used in the production of cord, tires and the like. Forexample, a straight mineral oil finish has little or no effect inconserving the strength of the yarn to give a strong cable, while asoftening agent yields 'improvements in strength running as high as 50%over cables formed from yarns not so finished. it would seem that suchfinishing of the yarn is essential for the production of a smooth,well-formed, compact cable which will have the maximum strengthobtainable from a plurality of twisted yarns. l

It is of course desirable that the yarn be lubricated to some extent toprevent breakage or other damage during handlingand if the softeningagent does not impart sufficient lubrication thereto, a suitablelubricant may be blended with the softening agent.

Tire cords and reinforcing cables and fabrics used in various bodiesformed of plastic material may be prepared from rayonl in the mannernoted above with numerous not heretofore obtainable advantages. Inaddition to the points of superiority already noted, the tendency ofrayon cord in tires to grow in service is prevented or minimized by theuse of the yarns of low elongation described above. It will be readilyseen that the tire structure will be adversely affected or the tire perse enlarges if the yarns used in producing the reinforcing cablesbecomes permanently elongated during use of the tire.

To better set forth' a comparison of the improvements of the variousfeatures of this invention the details of one specic process forproducing a rayon cable will be described without the additional stretchbut with the conditioning operation and other novel features merely byWay of exemplification. A soaking lye is ilrstv prenormal manner for twohours and is subjected to an' ageing temperature of 21 C. forapproximately 56 hours. Viscose having a cellulose content of '7.4% andalkali content of 7.3% is next formed therefrom, and it is permittedto`mature or ripen to 12.3 ammonium chloride index Whereupon theviscosity is approximately 40 seconds.- The viscose is then extrudedthrough a spinneret into a coagulating bath containing sulphuric acid,sodium sulphate, zinc sulphate and approximately 10% of magnesiumsulphate. The spinning bath is maintained at a temperature of 43 C. to45 C., and a higher temperature may be utilized if proper equipment isavailable to avoid evaporation problems encountered with the likelyimpairment to the health of the operators. The filaments thus formed areconducted from the bath and lhave a stretch impartedl thereto of 45% bypassing the same between two godets, and thence' to a spinning spoolthat has a takeup speed substantially equal to the peripheral speed ofthe second godet. This corresponds to the first part of the interruptedprocess. The spinning speed utilized is 'Il meters per minute, the yarnbeing of 275 deniers and having filaments. Yarn thus produced is washedacid free and then dried and it is nished by being further dried by thevacuum method. A solution of 0.6% Monopole Brilliant oil is caused topermeate the wound package and the package is subjected to dry vacuum toinsure uniform distribution of the finish. The package is 'thenadditionally dried on the spinning spool. After being dried, the yarn isthen twisted four turns per inch. The yarn in this condition is readyfor formation into cables and in tests which have been conducted todetermine the exibility of cables formed from such yarn, .uve of thethus formed yarns were twisted together to form a ply or intermediatestrand and three such strands were then twisted together to form acable. The herring or fatigue test of such a cable was 35,235 flexesbefore breaking and a cable similarly produced but in which the viscosewas formed entirely from wood pulp without the inclusion of cottonlinters and the coagulating bath did not have a high magnesium content,a fiexing test of 24,975 was determined. The same flexing test made withrespect to a cable formed of yarns which were not finished with MonopoleBrilliant oil or any of the other materials referred to above, had aexing test of only about 900. The fatigue or flexing tests wereconducted on a similar principle as that taught in an article by F. B.W. King and R. rIruesdale, published in The Textile Recorder, May 15,1923. v

The other physical characteristics of the yarn I Y are tabulated belowin order to show by way of comparison the improved results obtained.

Yam cable Dry Wet Dry elon- Wet elonstrength strength gation gationStrength Etia- Per cent Per cent Prepared from normal viscose 281 1l 1413 ,Per cmi; Prepared from normal viscose softening agent-.-. 281 162 1114 1s 9 4 Prepared according'to above example 318 185 12 l5 19,9 9Prepared according to above example additional 15% stretch y 340 207 12,5 23 a 5 pared from 18.3% alkali containing 0.6 or'0.7% hemicellulose.Alkali cellulose is next prepared and at least 25% of cotton linters isutilized with the remainder of the cellulose being derived from Thestrength of the yarn is given in grams per .100 denier and the strengthof the 'cable is given in pounds; in addition, the strength of both theyarn and cable was obtained by conditioning at wood pulp. The alkalicellulose is shredded in a 'I6 65% relative humidity.

Wet strength Wet elon- Dry elongation Dry gation strength Before 2ndstretch.. 5-l0% 2nd stretch. g '20% 2nd stretch..-

The importance of stretching after washing and subsequent proper:finishing to increase the cable strength, to prevent loss of strengthduring cabling, and to obtain a cable of low elongation is obvious fromthe preceding examples.

Yarns spun from a mixture of viscose solutions and casein solutions givecables of improved bonding properties with respect to rubber. Theproportions of viscose and casein used in producing the yarn may varyfrom a small proportion up to about 10% depending upon the propertieswhich the yarn is intended to possess but it is preferred that thecasein be present in amounts not exceeding by weight of the cellulose insolution or of the finished yarn. Such mixed yarns may be treated withformaldehyde or a suitable tanning agent during spinning or subsequentthereto in order to cause the casein content of the yarn to assume thedesired properties. Spinping baths particularly suited for use inmethods of preparing strong casein are disclosed at length in theapplication of J acokes, et al., Serial Number 246,466, led December 17,1938.

Additionally it has been found -that formaldehyde resin in particular,and other non-thermoplastic materials to some extent, may be added tolthe viscose for the purpose of aiding the bond between the rubber of thetire or the like and the reinforcing viscose cable. l

Yarn formed from mixtures of casinand viscose produce a strong yarnsuitable for cord construction for tires, belts and the like liiias'muchas these proteins cause unusually improved adhesion of the cables torubber. The cords for these purposes may be constructed from mixtures ofcasein fibers and viscose bers, yarn spun from a mixed solution ofcasein and viscose. It has been known to prepare casein-viscose mixturesfor spinning to produce a thread suitable for general textile purposesbut prior to the present invention it has not been considered possibleto prepare a mixed fiber having properties such as high strength, lowelongation, fiexibility and resiliency suitable for use in thepreparation of cord tires, belts and the like.

The preparation of casein-viscose solutions for the purpose of producingyarns may be carried out in any suitable manner. A preferred method forthe production of such solutions is to prepare a viscose solution bysoaking sheets of cellulose in alkali, pressing said sheets to removethe excess caustic and the more alkali soluble forms of cellulose,shredding the sheets impregnated with alkali, aging the shreddedmaterial to reduce the viscosity thereof, reacting the shredded alkalicellulose with carbon disulphide and dissolving the thus formed xanthatein dilute caustic soda to yield a viscose solution containing a littleover rI% cellulose. 'I'he viscose solution as thus pre pared is aged fora suitable period to improve the spinning characteristics and it is thenthoroughly mixed with casein, preferably denatured in the mannerdisclosed in the above noted application and dissolved in dilute alkali.A suitable` spinning composition as finally prepared is composed of:

f Per cent Cellulose A 'I Sodium hydroxidel V7 Casein ,12 Sulphur 2 1Based on the weight of the cellulose.

It has been found that especially high quality filaments and yarns areobtained with a solution which contains equal Aparts cellulose andsodium hydroxide to thecaustio. After the preparation of thecasein-,viscose mixture, it is aged for 24 hours, filtered and deaeratedunder strong vacuum for a prolonged period similar to the manner ofdeaerating the viscose solution as set forth in the above specificexample. The composition is then extruded into any of the conventionalbaths used for viscose, particularly when the casein content iscomparatively low. Suitable coagulating baths are described above. Whenthe composition being extruded contains a large quantity of casein, thecoagulating bath may be modied according'ly.

The viscose-casein filaments formed as above specified are drawn fromthe bath and they have a suitable stretch imparted thereto, for example,a stretch of 40%, after which they are formed into a cord or cable as inthe case of the viscose as above described. To prevent the stripping ofthe casein from the filament by washing operations prior to cabling, theyarn is given a preliminary washing with a dilute solution offormaldehyde or of other insolubilizing agents and it is then washedwith water. The yarn thus washed, and while still moist, is then givenan additional stretch before it is dried in any suitable manner.

Relatively small quantities of casein or other protein do not adverselyaffect the physical strength of the viscoseyarn but they do materiallyimprove its stability and adhesion to rubber. As will appear from theabove, the yarn formed of the viscose-casein mixture is subjected tosubstantially the same treatment and manipulation as the viscose yarnexcept for such modifications in the treating bathas are necessary.

In the utilization of this invention, it is extremely important that allapparatus, used in the preparation of the yarns, that contact with thesubstances entering into the vformation thereof, be composed of amaterial which resists corrosion and which will not contaminate saidsubstances. It has long been known that porcelain, nickel and the likeand stainless steel are suitable materials for use in constructing thefilter presses, conduits, and the like or as linings or coatingtherefor.

It is to be understood that while the discussion is generally directedto the preparation of filaments, it is intended to cover threads, yarns,cords, ribbons, foils, sheets or other products usually produced byextrusion or spinning. The invention has been described in detail inorder that those skilled in the art may practice the same, but it isobvious that it is not to be restricted to the specific examples setforth.

In using the expression up to the breaking point throughout thespecification andl claims, it is, of course, intended to mean that thethread is stretched just short of the breaking point.

What is claimed is:

high tenacity artificial yarn comprising a spinneret for deliveringfilaments to a coagulating bath, a washing bath, a device for collectingthe filaments, rotatable rollers operating at different peripheralspeeds intermediate said spinneret and said collecting device forstretching thefilaments, and means intermediate said stretching rollersand said collecting device for again stretching the filaments, saidsecond stretching means comprising rotatable rollers mounted in spacedrelation, and operating at different peripheral speeds, at least one ofthe rollers of the second stretching means being positioned within saidwashing bath.

2. An apparatus for producing low elongation, high tenacity artificialyarn comprising a spinneret for delivering filaments to a coagulatingbath, a device for collecting the laments, rotatable rollers operatingat dierent peripheral speeds intermediate said spinneret and saidcollecting device for stretching the filaments, and means intermediatesaid stretching rollers and said collecting device for again stretchingthe filaments, said second stretching means comprising freely rotatablerollers in mounted spaced re'- lation, said rollers having guidingsurfaces so arranged that when the filaments are passed alternately fromthe surface of one roller to the surface of another roller a pluralityof times, each succeeding guiding surface in the path of the filamentshas a greater diameter than the preceding one, whereby different linearspeeds are imparted to the filaments.

3. An apparatus for producing low elongation, high tenacity artificialyarn comprisingy a spinneret for delivering filaments to a coagulatingbath, a device for collecting the filaments, ro-

I tatable rollers operating at different peripheral speeds intermediatesaid spinneret and said collecting device for stretching the filaments,and means intermediate said stretching rollers and said collectingdevice for again stretching the filaments, said second stretching meanscomprising freely rotatable rollers in mounted spaced relation within abath, said rollers having guiding surfaces so arranged that when thelaments are passed alternately from the surface of one roller to thesurface of another roller a pluralityv of times, each succeeding guidingsurface in thev path of the mamentshas agrcater diameter-than thepreceding one, whereby different linear speeds are imparted to thefilaments. y

4. In the manufactureof high tenacity, low elongation viscose yarn, thesteps which comprise extruding a viscose solution into an acid bath thatcoagulates and partially regenerates th filaments formed therein,withdrawing the filaments from the bath and positively stretching thesame to substantially their breaking point prior to contact with asecond bath, thereafter passing the filaments through a washing bath andduring their said passage imparting a second stretch to said filamentsto substantially vtheir breaking point as their regeneration 'conpriorto contact with a second bath, thereafter passing the filaments througha washing bath and during their said passage impartinga second stretchto said filaments to-substantiaily their breaking point as theirregeneration continues substantially to completion, said second stretchbeing imparted to said filaments independently of the first mentionedstretch and the summation of the stretches totaling more than 70%.

v6. In the manufacture of high tenacity, -low elongation viscose yarn,the steps which comprise extruding a viscose solution into an acid baththat coagulates and partially regenerates the filaments formed therein,withdrawing the 40 filaments from the bath and positivelystretchsubstantially to completion, said second stretch being impartedto said laments yindependently of the rst mentioned stretch, and finallycollect ing the laments without releasing the tension thereon.

GILBERT I. THURMOND.

